1. Field of the Invention
The present invention relates to a magnetic recording medium, a method of manufacturing therefor, and a magnetic read/write apparatus that uses the magnetic recording medium.
2. Description of the Related Art
The in-plane magnetic recording medium has been widely used wherein the axis of easy magnetization in a magnetic film is generally oriented parallel to the substrate. In the in-plane magnetic recording medium, there is a possibility of medium noise increasing under the influence of diamagnetism in the boundary of recording pits when the recording density is increased. In the perpendicular magnetic recording medium of which axis of easy magnetization in the magnetic film is generally oriented perpendicular to a substrate, in contrast, recording magnetic domains that have clear boundaries can be formed due to smaller influence of diamagnetism in the boundary of recording pits even when the recording density is increased, and therefore, thermal decay and noise characteristics can be improved, resulting in much attention to the perpendicular magnetic recording medium.
Recently, there has been increasing demands for high-density recording in the magnetic recording medium. For this reason, such a magnetic recording medium has been proposed as a layer made of a soft magnetic material, called a soft back layer, is provided between a perpendicular magnetization film that serves as a recording layer and a substrate so as to improve the efficiency of the flow or the magnetic flux between a single pole type head and the magnetic recording medium, in order to use the single pole type head that has high capability of writing in the perpendicular magnetization film.
However, even when the soft back layer is provided, the magnetic recording medium does not have satisfactory performance in the read/write characteristics, thermal stability and the resolution of recording, and therefore a magnetic recording medium that is better in these characteristics has been required.
Japanese Patent No. 2769511 proposes to control the orientation dispersion angle xcex94xcex850 of the c axis of the crystal orientation promotion layer within 7 degrees, while Japanese Patent Application, First Publication No. Hei 6-76260 proposes to control the orientation dispersion angle xcex94xcex850 of the c axis of the fcc structure within 10 degrees.
However, it is not sufficient to control the orientation dispersion angle of the crystal orientation promotion layer within a particular angle, for the purpose of improving the characteristics of the perpendicular magnetization film.
Taking account of the growth in the early stage of forming the perpendicular magnetization film at the interface between the crystal orientation promotion layer and the perpendicular magnetization film, there is a possibility of the crystal grain diameter of the magnetic film increasing when the difference in orientation between the crystal orientation promotion layer and the perpendicular magnetization film is small. When the difference in orientation is too large, on the other hand, the portion of the perpendicular magnetization film provided by the early growth becomes too thick, leading to deterioration in the read/write characteristics and in the thermal stability.
When the orientation dispersion is controlled to proper values in the crystal orientation promotion layer and in the perpendicular magnetization film, it is made possible to promote the nucleation during the growth of the perpendicular magnetization film and to form microcrystals, while keeping the portion formed by the early growth from becoming thicker, thereby preventing the thermal stability from deteriorating.
Under the above-described circumstances, the present invention has been made, and an object thereof is to provide a magnetic recording medium, that is capable of recording and replaying at a higher density by improving the read/write characteristics, a method of manufacturing therefor, and a magnetic read/write apparatus.
The magnetic recording medium of the present invention comprises at least a soft magnetic undercoat film made of a soft magnetic material, an orientation control film that controls the orientation of a film provided directly above, a perpendicular magnetization film of which axis of easy magnetization is generally oriented perpendicular to a substrate, and a protective film, that are provided on a non-magnetic substrate, wherein the orientation control film has an hcp structure and, at the same time, xcex94xcex850 of the (0002) orientation plane is set within a range from 3 to 10 degrees and a difference (xcex94xcex850 (mag)xe2x88x92xcex94xcex850 (ori)) between xcex94xcex850 (ori) of the orientation control film and xcex94xcex850 (mag) of the perpendicular magnetization film is set within a range from 1 to 8 degrees.
The orientation control film can be made in a construction that contains equal to or greater than 50 at % of one or more kinds of elements selected from Ti, Zn, Y, Zr, Ru, Re, Gd, Tb and Co.
The orientation control film can be made in a construction that contains one or more kinds of elements selected from V, Cr, Mn, Fe, Co and Ni.
The orientation control film can be made in a construction that contains one or more kinds of elements selected from B, C, N, O and P.
According to the present invention, such a construction may be employed as a non-magnetic intermediate film is provided between the orientation control film and the perpendicular magnetization film, while the non-magnetic intermediate film is made of a material containing 40 to 70 at % of Co.
The orientation control film can be provided so as to have granular structure and have a mean crystal grain diameter from 4 to 20 nm.
The magnetic recording medium of the present invention may have such a construction that comprises at least a soft magnetic undercoat film made of a soft magnetic material, an orientation control film that controls the orientation of a film provided directly above, a perpendicular magnetization film of which axis of easy magnetization is generally oriented perpendicular to a substrate, and a protective film, that are provided on a non-magnetic substrate, wherein the orientation control film has an fcc structure and, at the same time, xcex94xcex850 of the (111) orientation plane is set within a range from 3 to 10 degrees and a difference (xcex94xcex850 (mag)xe2x88x92xcex94xcex850 (ori)) between xcex94xcex850 (ori) of the orientation control film and xcex94xcex850 (mag) of the perpendicular magnetization film is set within a range from 1 to 8 degrees.
Negative nucleation field (xe2x88x92Hn) of the perpendicular magnetization film is preferably equal to or higher than 0(Oe).
The method of manufacturing the magnetic recording medium of the present invention comprises forming at least a soft magnetic undercoat film made of a soft magnetic material, an orientation control film that controls the orientation of a film provided right above, a perpendicular magnetization film of which axis of easy magnetization is generally oriented perpendicular to the substrate, and a protective film, on the non-magnetic substrate, while controlling so that the orientation control film has an hcp structure and, at the same time, xcex94xcex850 of the (0002) orientation plane is set within a range from 3 to 10 degrees and the difference (xcex94xcex850 (mag)xe2x88x92xcex94xcex850 (ori) between xcex94xcex850 (ori) of the orientation control film and xcex94xcex850 (mag) of the perpendicular magnetization film is set within a range from 1 to 8 degrees.
The magnetic read/write apparatus of the present invention comprises the magnetic recording medium and a magnetic head that records information on the magnetic recording medium and replays the information therefrom, wherein the magnetic recording medium comprises at least the soft magnetic undercoat film made of a soft magnetic material, the orientation control film that controls the orientation of a film provided right above, the perpendicular magnetization film of which axis of easy magnetization is generally oriented perpendicular to the substrate and the protective film that are provided on the non-magnetic substrate, and the orientation control film has an hcp structure and, at the same time, xcex94xcex850 of the (0002) orientation plane is set within a range from 3 to 10 degrees and the difference (xcex94xcex850 (mag)xe2x88x92xcex94xcex850 (ori)) between xcex94xcex850 (ori) of the orientation control film and xcex94xcex850 (mag) of the perpendicular magnetization film is set within a range from 1 to 8 degrees.